Photoneutron cross section measurements on ^208Pb in the Giant Dipole Resonance region

Photoneutron reactions on ^208Pb in the Giant Dipole Resonance energy region have been investigated at the -ray beam line of the NewSUBARU facility in Japan. The measurements made use of quasi-monochromatic laser Compton backscattering -ray beams in a broad energy range, from the neutron threshold up to 38 MeV, and of a flat-efficiency moderated ³He neutron detection system along with associated neutron-multiplicity sorting methods. We report absolute cross sections and mean photoneutron energies for the ^208Pb (, \, inX) reactions with i~=~1 to 4. The fine structure present in the ^208Pb (, \, n) cross sections at incident energies lower than 13~MeV has been observed. The photoabsorption cross section has been obtained as the sum of the (, \, inX) reaction cross sections. By reproducing the measured ring-ratio values at excitation energies below the two neutron separation energy, we were able to extract estimations on the ^208Pb (, \, n) photoneutron energy spectra and on the partial photoneutron cross sections for leaving the residual ^207Pb in its ground and first two excited states. The present results are compared with data from the literature and statistical model calculations.